Diapositiva 1
Casting of Metals and Alloys in 2000 and BeyondPresented toDr.
N.C. UpadhyayAssociate ProfessorDept. of Metallurgical and
Materials Engg. MNIT Jaipur
Presented byBhavanish Kumar Singh2012umt1402 B.Tech 4th
YearDept. of Metallurgical and Materials Engineering
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Introduction
Casting is a manufacturing process by which a liquid material is
usually poured into a mold, which contains a hollow cavity of the
desired shape, and then allowed to solidify.Advantages of
casting1.Lowest cost method for manufacturing complex
parts2.Reduces part count, weight, machining3.Reduces manufacturing
space and inventory
Vacancies in the market1.Shortage of Skilled Technicians and
competition because of globalization2.Requirement of more capable
computer programs.3.Much of development in metal casting driven by
solidification simulation packages.
Benefits of Computer Simulation Packages Automotive and aircraft
industriesHigh degree of accuracyPredict the cast structure
depending on cast parametersStatic and dynamic properties of the
component can be predicted and compared with designers requirement
Identify Casting Defects and so Non Destructive 6.Evaluation is
done.7.Reduce life cycle costs of casting8.Minimized machining
Metal Shaping RoutesFinal properties of a casting greatly
influenced by casting and moulding process alone .Major
contribution to casting industry new developments given by
Automotive industry.For e.g.1.Aluminum Suspension parts used in
steering as its first production application2.Dashboard in Plymouth
Prowler is die cast Mg alloy
Car Steering Suspension parts
Plymouth Prowler
Squeeze casting, also known as liquid metal forging, is a
combination of casting and forging process. Both ferrous and
non-ferrous materials can be produced using this method. Slow
Ingate velocities with minimal turbulence and slow
application(50-100mm/min) of high pressures (35-105 MPa)
Low porosityHigh integrityHeat treatable Two typesDirect
application of pressure to the piston, which contacts the molten
metal. Indirect the melt is forced from a system of runners to the
mould cavity gate.
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Lost-foam casting (LFC) or Evaporative-pattern casting process
i.e. Similar to investment casting except foam is used for the
pattern instead of wax. 1.Advantage of the low boiling point of
foam by removing the need to melt the wax out of the
mold.2.Applications: Making truck, pipe, and automotive high
volumecomponentsCommonly cast metals include cast irons, aluminium
alloys. steels, and nickel alloys;less frequently stainless steels
and copper alloys are also cast.
Shell MouldingShell mold casting or shell molding is a metal
casting process in manufacturing industry in which the mold is a
thin hardened shell of sand and thermosetting resin binder, backed
up by some other material. Shell mold casting is particularly
suitable for steel castings The sand mixture is poured or blown
over the hot casting pattern. Reaction of the thermosetting resin
with the hot metal pattern, a thin shell forms on the surface of
the pattern.
The excess "loose" sand is then removed, leaving the shell and
pattern. The shell and pattern are then placed in an oven for a
short period of time, (minutes),. the hardened shell is separated
from the casting pattern by way of ejector pins Two of these
hardened shells, each representing half the mold for the casting,
are assembled together either by gluing or clamping.
Counter Gravity CastingProduction PartsCast Stainless Steel
ExhaustCast Steel Contoured Camshaft, Brake Rotor, Primary Pump
Body, Crank Case for Air compressors, Bearing case for Industrial
machinery
Differential pressure sand casting: Alternative to conventional
gravity casting.Create differential pressure by evacuating the
mould cavity, in contrast to most processes, Relatively SimpleCan
be used for small batch melting operations Ex. Light alloys
aerospace foundries.
Flaskless vertically parted green sand moulding
In flaskless moulding, no flask is used for supporting the
moulding sand; the mould itself is made sufficiently strong to bear
the liquid metal pressure.Two types:1.Vertical Parting Flaskless
Moulding (DISAMATIC) 2.Horizontal Parting Flaskless Moulding
(Website: www.ijrdet.com (ISSN 2347 - 6435 (Online) Volume 2,
Issue 4, April 2014) )Fig: Vertical Parting Flaskless Moulding
(DISAMATIC)
Advantages of Flaskless Moulding It does not use flasks, which
avoids a need of their transporting, storing and maintaining. No
repair expenditure on flasks By adopting aeration sand filling
technology, energy saving and noise reduction have been achieved
Stable pattern draw is secured by automatic pattern spray Minimize
turbulence and porosity in casting
Freeze Cast Process(FCP): By subjecting an aqueous slurry to a
directional temperature gradient crystals will nucleate on one side
of the slurry Steps:Making a solid master pattern by traditional
machining and materials, or by any one of the state of the art
pattern generating methods such as stereo lithography, laminated
object manufacturing(LOM), selective laser sintering(SLS)2. Making
rubber moulds using silicon rubber or urethane polysulfide, which
are available in liquid form, from the master pattern.3. Pouring
water containing additives into rubber mould and freeze the water4.
Stripping the ice pattern5. Repeated stripping of the ice pattern
into refrigerated ethyl (alcohol) silicate slurry
6. Exposing the shell containing ice pattern to slow heating
pouring out water and then firing of shell.7. Pouring of molten
metal into the shell solidify to get final casting.
Metals and alloys like gray iron, ductile iron, steel, aluminium
and copper.
Significance:Near net shape castings, fast pattern making,
pattern is not burned out
Not Suitable for large casting, flat parts with thin walls.
Semisolid ProcessingThixomolding is one step process for making
near net shape castingsE.g. Mostly Magnesium and Zinc alloy parts.
Electronics and communication, Automotive shift cams, throttle
bodies, etc.
Notebook computer casesDigital camera bodies
Hand held power tools
Hot Isostatic Pressing (HIP)Components are subjected to the
simultaneous application of heat and high pressure in an inert gas
medium.Pressure by gas makes it Isostatic and uniform and leading
to plastic state collapses any left voids.Use as precision
castings.Complex shapes can be formed without expensive
tooling.
Plasma Cupola
Plasma Cupola Pilot Plant at General MotorsFirst used for the
production of Cast iron engine blocks.Cost effective melting in
difficult to melt raw materials such as Loose cast iron borings and
production of world class automotive castingsMelting and Melt
Treatments
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Mg HeatingHumid conditions must be avoided and mixing gases must
contain less than 0.1 %moisture.SF6 base gases and SO2 air mixtures
are used as oxide barrier for melting Mg and its alloys but are
very harmful for environment even in ppm
Ultrasonic degassing of Al melt
Water vapour and Al2O3 reacts and H2 evolves causing
microstructure degradation and embrittlementSo Ultrasonic
(cavitational) degassing more effective than fluxes/argon/vacuum
degassing in lowering the hydrogen content of Al melt.10% increase
in tensile strength(UTS) and 80% more % elongationattained with
combined vacuum and ultrasonic treatment.Produce non dendritic
microstructure& very low H2content
Ultrasonic vibrationAl Melt
Running, Gating and RiseringDesigned to introduce clean, dross-
free, tranquil metal into the mould cavity and continue to feed
liquid metal to casting as it solidifies.Gating system should
ensure non-turbulent pouring at lowest velocityDistance between
sprue and ingates should be maximized to allow time for dross to
float out and trapped at top surface of the runner bar.American
Foundrymens Society, USA found a software simulation package called
AFS 3D solid model system that provides data related to casting
quality without manufacturing the casting.Finite Difference Method
(FDM) used to find energy during pouring, including mixing and
turbulence during mixing.
ToolingComputer Tomography (CT) for reverse engineering and
Rapid proto typing (RP) techniques are used for producing patterns
for tools.Rapid pattern making gives the foundry new possibilities
for the fast production of metal prototypes and series parts.Rapid
tooling for sand casting can be made using Computer numerically
Controlled (CNC) machining of non-ferrous pattern materials By
using patterns created directly in rapid prototyping machines.
Development and usage of New Alloys and materialsTodays NeedCost
effective in global economyIntegrated approach incorporating
materials scienceProcess technology Design and Performance of the
product is must. For e.g.. Use of New high grade H13 tool steel for
shot sleeves and other die components of aluminium pressure die
casting machine has yielded a 10-20 % enhanced die life and huge
savings.Protein based ,water soluble binder for sand casting has
been developed as also environment friendly.Used or unused cores
can be placed in a water bath and the resin can be reclaimed.Lower
cost Aluminium metal matrix composites (AMMC) expanded its market
potential e.g. in automobiles parts like brake rotors, drums,
calipers and pads back plated, Cylinder liners, Steering links,
Clutch Plates, Structural Oil Pans, Brackets, Suspension arms,
etc.
Reuse, Recycling And Eco friendliness Increasing pressure to
improve its environmental performance to meet sustainable
development Reuse of foundry by-products Cryogenic sand reclamation
could be a potential route of the future (liquid N2 is used to
reduce sand temperature to as low as -80 C which separates sand
from other valuable constituents)Recycled aluminium for making
automotive Al castings in US was around 63% in 1999.Process
control, major tool for waste reduction generally a little or no
capital cost and quality improvement.Foundries are most polluting
industry
ConclusionFoundries of tomorrow have to exploreNear net shape
processConcept of cast-to-fill and HIP-to-density for critical
componentsConsortium/ co-operative approach towards
R&DBeneficial reuse optionsUse newer tools such as computer
simulation, expert system, neural net work, etc.Reduction of
production cost by better controlConverting into an ecofriendly
industry.
References
Casting of Metals and Alloys in 2000 and BeyondR.M Pillai, B.C.
Pai and K.G. SatyanarayanaRegional Research Laboratory, Council of
Scientific and Industrial Research, Thiruvananthapuram-695019